It takes three months for a behavior to become a habit, so we've mapped out a plan to keep you on track through every obstacle.

New Year’s Eve

You think: “I’m going to spend less, work out more and get promoted.” Creating a resolution that’s too big or too vague sets you up for failure. The first key to success: zeroing in on one goal, not three. Then do a quick reality check. “Look at the level of commitment it will require to achieve, and consider if you’ll be able to match it,” says Larry Kubiak, Ph.D., director of psychological services at Tallahassee Memorial Hospital. Are you really going to be able to swear off chocolate completely? Unlikely. Limiting your Hershey’s Kisses eating to a few times a week would be much more achievable. Which brings us to the second success tip: getting specific. “The more detailed you can be—’I’m going to save $30 a week by eating out one fewer meal’—the less difficult it is to stay focused on what you have to do to succeed,” Kubiak says.

Week 1

You think: “I’m staying mum about my goal in case I fail.” Nearly one quarter of respondents in a SELF.com poll say they keep their New Year’s goal on the down low. Bad idea. We’re more likely to achieve our resolutions when we make them public, according to research conducted at the University of Hertfordshire. “Sharing our goals holds us accountable, so it’s harder to back out,” says John Norcross, Ph.D., professor of psychology at the University of Scranton. (And if you do stumble, no one will judge. We’ve all been there!) Enlist a few friends, and sign up at Stickk.com. You enter your goal, then send pals reports on your progress: “I lost 1 1/2 pounds this week!” You’ll need to own up if you fall behind, but they can send encouraging notes to get you back on course.

Week 3

You think: “My resolution is one more thing on my to-do list.” At first, your goal was new and exciting, so you were inspired to make time for it; three weeks in, the novelty has worn off, says Emanuel Maidenberg, Ph.D., associate clinical professor of psychiatry at the University of California in Los Angeles. “If each morning you have to find a way to make your goal happen, you’re more likely to decide based on whether you feel like doing it, which we rarely do,” Maidenberg says. Plot out a monthly budget or schedule a week’s worth of workouts each Sunday so you don’t have to think about how to fit it all in. And attach your goal to another activity. For instance, if you want to meditate more, plan a nightly session for right after brushing your teeth. Done!

Week 4

You think: “I’m not seeing big results. I might as well give up.” If your focus is on the endgame, it’s easy to feel discouraged when progress plateaus around the one-month mark, Kubiak says. That’s why it’s crucial to recognize and reward the smaller successes along the way. Rather than waiting until you’ve shed all 10 pounds, give yourself a mini “Yay, me!” celebration each time you drop 2. If your goal is to run a half marathon, don’t save the party for the finish line. After each long run, reward yourself with a good book, new music or a night out with friends. To help you track important milestones along the way, use a journal: Self-monitoring has been shown to bolster resolve and keep you motivated by reminding you how far you’ve come.

Week 6

You think: “Crap. I slipped up. Now what do I do?” You’re in good company: “Having a lapse is common. In fact, 75 percent of resolution makers slip up within the first two months,” Norcross says. What really matters is how you handle it; 24 percent of Self.com respondents say they spend several days feeling guilty over their misstep; 61 percent say they acknowledge the screwup but get right back on track. Guess which group is more likely to succeed? “One setback shouldn’t undo all your efforts. Instead of stewing, figure out how to prevent the slip from happening again,” Norcross says. Blew this week’s savings on boots from Zappos? (We get it: free shipping!) Find a way to recoup what you spent: At Zappos, returns are free, too!

Bill Diodato

Week 8

You think: “I need others to push me to… [fill in the blank].” Asking people for support is smart, but to make your resolution stick, now is the time to learn how to be your own cheerleader. In fact, relying too heavily on a pal or family member to get you to do something can actually decrease your motivation to work toward your goals, a study in Psychological Science finds. Your boyfriend might be great at getting you out of bed for your morning jog, but what happens when he’s out of town? Without any motivation to hit the treadmill on your own, you and the snooze button will become BFFs. To remind yourself why this goal is important to you, write little notes and post them where you’ll see them—your desk, the mirror and the snooze button!

Week 9

You think: “I’m doing so well, I can stop keeping track.” It’s awesome that you’ve made it this far, and you totally deserve a little celebration, but with the finish line in sight, now is not the time to slow down. “Once your behavior starts to feel routine, it’s easy to assume you have this in the bag and can let down your guard,” Norcross says. “But that’s when you become vulnerable to missteps.” You may think that because you haven’t smoked in more than two months, you can lift your ban on going out with friends who do, or that you can stop keeping a food log because you’ve got the diet down. But those techniques were crucial to your success up to this point, and taking them away can dissolve your resolve. “Whatever you’re doing is working, so don’t stop!” Norcross urges.

Week 12

You did it! Happy new YOU! Now that you’ve cemented your healthy new habit, you can really celebrate! Just don’t get so carried away—ice cream every night! two weeks without a trip to the gym!—that you undo all your hard work. It’s time to figure out what your maintenance plan will be, so you’ll still be going strong three months from now. “External motivators, such as losing weight before a high school reunion, are typically what jump-start our resolutions,” Norcross says. “But they don’t sustain us over time.” For that, you have to find motivators that are personally meaningful: how great you feel after finishing that 5-mile run, or how much more energy and confidence you’ve had since you dropped the weight. This year’s resolution: achieved. Next up: 2013!